This application requests support for a Keystone Symposia meeting entitled Stem Cells in Development, Tissue Homeostasis, and Disease, organized by Drs. Ronald McKay, Elaine Fuchs, and Thea Tlsty, which will be held in Santa Fe, New Mexico from January 30 - February 4, 2011. This meeting is focused on the mechanisms controlling stem cells throughout life. More specifically, the presentations will define the different pluripotent cells in the early embryo, the signals that lead them into the many distinct cell types that cooperate to form an adult organism, the contributions of stem cells to diseases such as cancer, and how stem cells are being used as models and therapeutics for disease. An exciting aspect of the field is that as we define the shared mechanisms controlling different tissues, we are generating an integrated view of human development: indeed, this meeting is designed to present key advances that are leading to a systematic understanding of the biology of human tissues throughout life. The presentations are designed to serve as a strong foundation and as jumping-off points for critical discussion by all participants of questions, controversies, gaps, and new technologies that are allowing us to identify the central regulators of development and to treat disease. PROJECT NARRATIVE: Deep interest in stem cells follows from their place in normal development and repair, from growing evidence for their role in diseases such as cancer and aging, and from their promise in treating disease. While much progress has been made in revealing mechanisms for maintaining and differentiating stem cells, as well as how they might contribute to disease, we are still at the early stages of developing a more systematic understanding of stem cells. The Keystone Symposia meeting on Stem Cells in Development, Tissue Homeostasis, and Disease aims to provide a forum for sharing and critically discussing the latest results, as well as for developing a more comprehensive picture of stem cells in health and disease.